异戊烯与甲醇成醚反应机理的量子化学研究

对2-甲基-1-丁烯、2-甲基-2-丁烯与甲醇反应生成甲基叔戊基醚的反应历程进行了量子化学研究, 结果表明, 反应过程包括两个基元步骤: 2-甲基-1-丁烯和2-甲基-2-丁烯与氢离子作用生成碳正离子, 活化能分别为E1=2.26 kJ/mol, E2=7.72 kJ/mol; 甲醇与叔碳正离子反应成醚, 活化能为E3=1.29 kJ/mol, 碳正离子的生成是反应的速控步骤. 2-甲基-1-丁烯与2-甲基-2-丁烯相互转化的异构化活化能分别为E'1=4.40 kJ/mol, E'2=63.11 kJ/mol, 高于成醚的活化能, 反应体系不发生烯烃相互转化的异构化反应.

Quantum Chemistry Research in Etherification of Isoamylene and Methanol

The mechanism of the reaction of 2-methyl-1-butene and 2-methyl-2-butene with methanol to yield TAME was theoretically studied by ab-initio H-F/6-31G*. The results show that the reaction includes two elementary reactions. First, isoamylene reacts with proton to produce tert-carbonium intermediate, then the intermediate reacts with methanol to produce the final product TAME. The activation energy of the resulting tert-carbonium from 2-methyl-1-butene and 2-methyl-2-butene are E1=2.26 kJ/mol, E2=7.72 kJ/mol respectively. The activation energy of the resulting TAME from methanol and tert-carbonium is E3=1.29 kJ/mol, so the formation of tert-carbonium is the rate-determining step, and the rate of etherification of 2-methyl-1-butene is quicker. For both 2-methyl-1-butene and 2-methyl-2-butene translate into tert-carbonium intermediate under the acidic condition, and the intermediate need to overcome E'1=4.40 kJ/mol, E'2=63.11 kJ/mol when it translate into 2-methyl-1-butene and 2-methyl-2-butene again, so it is very hard for it to translate into alkenes again. The isomerization of different alkenes didn't exist in this reaction.